systemMonitor: update for gnome-shell master

Reparent the message tray menu button so that the indicators
don't cover it.
apps-menu: fix for gnome-shell master

PopupMenu.isEmpty() only checks for regular menu items, which
the application menu doesn't use, so we need a fake implementation.
Bump version to 3.9.92

To go along GNOME Shell 3.9.92